Oliver Peoples 523 - Brad Pitt - Fight Club
In Fight Club, Brad Pitt wears three different types of sunglasses in the movie (all by Oliver Peoples: the Aero, the OP 523, and the Sunset, respectively). The OP-523 is by far the most popular (and hard to get!). Check eBay where you can usually find a few pair for very high prices.
Alternative sunglasses on Amazon
On Amazon you can find an affordable alternative, the Fight Soap Salesman Red Sunglasses ($17).
10th anniversary limited release
Celebrating the movie Fight Club's 10th anniversary, Oliver Peoples re-released Tyler Durden's signature sunglasses in 2009. The 523, out of production since 2000, was available for a limited time in two color options: Silver frame with Blood-Red glasses and Gold frame with Orange glasses. Only 75 of each will be sold, so this will also be an instant collector's item.
These glasses were exclusively available for purchase on the Oliver Peoples website and in Oliver Peoples boutiques.
Reference: Oliver Peoples 523, red lens